The present invention relates to a method of producing a protective gas consisting of 0.0010-0.100 percent by volume of nitric oxide, 0-90 percent by volume helium, 0-5 percent by volume hydrogen, 0-50 percent by volume carbon dioxide and the remainder argon, and also to a condensed gas mixture for the production of said protective gas.
In electric gas-arc welding processes there is often used a protective gas in the form of a gas mixture consisting of or comprising argon and nitric oxide. The protective gas mixture or protective gas may also include carbon dioxide, helium and/or hydrogen. To large consumers of protective gases, these gases containing nitric oxide, there is at present delivered a gas pre-mixture, a master gas, consisting of a nitric oxide in argon under high pressure, this gas being delivered in conventional steel bottles. The proportion of nitric oxide present is normally from 1-5 percent by volume, for instance 1.8 percent by volume. The desired protective gas is then produced by mixing the various gases with the gas pre-mixture to the composition desired. The amount of nitric oxide present in the final protective gas is normally at most 0.030 percent by volume.
Since nitric oxide is a poisonous gas, it is desirable to use lower proportions of nitric oxide in the master gas than those used hitherto. This results in higher transportation costs, since it is necessary to transport to the consumer more gas bottles containing master gas at unchanged protective gas consumption.
Another drawback with the master gas is that when preparing a protective gas it is necessary to supply additional argon in order to reach the desired final concentration of argon in the protective gas produced.